Method of making a resistance element



Feb. 18, 1 930. -s. RUBEN I v 1,747,649

METHOD OF MAKING A RESISTANCE ELEMENT Filed Jan. 5, 1929 aubentoz M/VUE L RUBEN 35 M au Patented Feb. 18, 1930 UNITED STATES SAMUEL RUBEN, OF NEW YORK, N. Y., ASSIGNOR TO RUBEN PATENTS COMPANY, OF

I NEW YORK, N. Y., A CORPORATION OF DELAWARE METHOD OF MARIN G A RESISTANCE ELEMENT Application filed January 5, 1929. Serial No. 330,608.

This invention relates to a method of making a resistance element and more particularly it relates to a method of applying a resistance coating upon the surface of a conductive member of a resistance device employing surface pressure changes for current control.

The object of the invention is the provision of a resistance element for controlling current between a low minimum and a relatively high maximum value in accordance with pressure variations between the elements.

It is old in the art to employ a carbon disc as the resistance element between conductive plates in a variable pressure resistance device, in the use of which various disadvantages exist, such as fragility and the relatively hi h resistance at maximum pressure, due to tie necessary thickness of the disc material.

I have found that highly satisfactory results are obtained in varlable pressure resistance devices in which relatively high temperatures develop, by employing as the resistance element a mixture of gas carbon and a suitable inorganic binder apphedas'a coating upon conductive pllites, such as iron or aluminum, which is then dried and heated to effect partial volatilization of the binder, leaving a hard substance, and thereafter compressed. In this way is obtained the desired even distribution of a durable, adherent compressed coating which has a hard, smooth surface, insurin evenly distributed surface contact with a li e coating upon another conductive plate or directly with such a plate, thereby preventing current localization. The thickness of the coating is determined by the energy to be applied. In a device employing a metal coating so produced the'resistance value at maximum pressure is very low, due to the metal base and the thin layer of the resistance material.

The preferred coating consists of a mixture of gas carbon, and an inorganic binder applied to a thoroughly cms'ifface. After drying, the metal disc with its coating is subjected to a temperature of approximately 500 C. and then passed between rollers com ressing the coating and reducing its thic mess, and producing a smooth surface of uniform thickness. A preferred mixture is as carbon with 30% silicate. Such a coat- 1%g Has Been found to have greater negative pressure resistance than that of a graphite coating or of the carbon discs.

For a better understanding of the invention reference is made to the accompanying drawings which illustrate one embodiment of the invention. In Figs. 1 and 2, C represents the carbon coating mixture applied to opposite surfaces of the aluminum plate P.

\Vhat I claim is: v

1. The method of making an element for a pressure controlled rheostat, which consists inapplying to the surface of a conductive body a mixture containing gas carbon and an inorganic binder, drying the coating, heating it to approximately 500 C. and passing the coated body between compression rollers.

2. The method of making a resistance element for a pressure controlled rheostat, which consists in applying to the surface of a metallic body a layer of gas carbon mixed with an inorganic binder, partiall volatilizing the binder and compressing tie coated element so as to produce a uniformly distributed layer of the resistance metal. 7

3. The method of making a resistance element for a pressure controlled rheostat, which consists in coating the surface of a conductive bod with a mixture containing gas carbon an a silicate and heating the coating until a partial volatilization of the silicate occurs, and compressing the coating.

4. The method of making a resistance element for a pressure controlled rheostat which consists in coating the surface of a conductive body with a mixture containing 70% gas carbon and 30% silicate heating the coating until a partial volatilization of the silicate occurs and compressing the coating.

In testimony whereof SAMUEL RUBEN has signed his name to this specification this 27th day of December, 1928.

. SAMUEL RUBEN.

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